Pneumatic hammer



Patented July l, 1930l y UNITED STATES PATENTA crete EDWARD W. srEvENs, E DETROIT, MICHIGAN Assrenon To CHICAGO PEEUMATIC TooLCoMrANY, CE` NEW YCEK, n. Y., A CoEroEATIoN oF NEW JERSEYK l EiviiunuArIc` HAMMER Y Application filed October 1, 1926. Serial IIa-138,862.

This invention relates to Huid pressure percussive tools and more specifically to large pneumatic hammers used in demolition work as in cutting oif bolt and. rivet heads. Such toolsv are commonly referred to asV rivet cutting guns and'usually require on account of their size :and .weight at` least two men to operate, `one to direct* the demolishing end of thegun and the other to control the m0-y tive fluid. I 4

Tools of the type described strike asingle blow in one position ofthe throttle handle which must then bemoved to a different position to return the hammer pistonfor the next blow. In order that. the blow may be delivered with fullforce it is the usual practice to provide a largeI permanently open vent port in the `cylinder wall. about an inch back of the piston when the latterris in its impacting position. This open vent necessitates the use of a large amountof motive fluid to return the piston,'so that `such tools are costly to operate in the matter of air consumption.

One object of the present inventionis to devise a tool of the described type which requires but littlemotive -fluid for the b-ack stroke of the piston Iwithout interferring with a free forward. or power stroke. y.Another objectisto make'thetool of `simple design in order to keep its cost within practical limits. Other objects will be` apparent from'thejdetailed description which follows.

In order to illustrate the invention one concrete embodiment thereof is shown in the accompanying drawings in which :y`

Fig.` 1 is a side elevational view, partly in section, of an improved form'of rivet cutting gun; v

Fig. 2 is a view similar to Fig. 1 showing the operative parts indifferent positions.

The tool shown comprises av cylinder 3 having secured thereto a front head 4 receiving the shank end 5 'of the Working tool and a back head 6 having a transverse bore receiving the control valve 7 arranged to be manually operated by a handle 8. `Valve 7 controls admission and exhaust ports for the motive fluid to effect the reciprocations Within cylinderlS of the hammer piston 9,'which imparts its yblow to the working tool 5 and i which; is arranged to becushioned on its rearward stroke by a spring 10. A pressure fluid supply pipe 11 attached to back headA 6 supplies motiveliuid to; valve 7 through a port 12. Back head 6 alsoprovidesa large exhaust port 13,Y a small exhaustport 14, a large port 15 opening. into the rear end. of the piston chamber, and a small port 16-connected to front head 1 by a `flexible conductor or pipe 17 which communicates with a passage 18 opening into auxiliary .valve chamber 19. A cup valve 20 having a small port21 therethrough is arranged for limited reciprocatoryT movement in chamber 19 kwhich chamber is closed. at its `outer end by a screw plug22 having a projection 22a` serving as astop for Vvalve 20. The forward end of the valvefchamber has an annular series of vvent ports 23 `controlled bya .valve 20 andthe valve chamber communicates with the front end of the piston chamber by a port 24.

jThe operation of the tool is as follows: With Ythe parts `in Athe position shown in Fig. l piston 9 is on its rearwardstroke.. A iiat 7a on: valve 7 establishes communication between supplyport 12and port 16, thereby directing motive iiuid into.: valve chamber L9 moving valve 2O to the position shown (if `not already in this position),.the pressureV fluid passing in limited amount through valve v'port `21 into the forward `end of .the pistony chamber to drive piston 9 rearwardly. Passage 18 being largerlthan port 21 insures y a greater pressure in the valve chamber 19 than in the piston 'chamber` so that v valve` 20 is retained4 in the positionshown. .The rearward end of Athe piston chamber is meantime open toexhaust by reason of groove 7 b in valve 7 establishing connection between ports 15 and 113. To reverse the movement of the piston valve `handle 8 is moved to the forward position shown in Fig. 2 whereuponports 12 and: 15l are connected by a transverse bore 7 c. in valve 7, thereby directing motive fluid in full volume and pressure behind pis-ton 9. At the` same time ilat 7a establishes connection lbetween ports v16 and 14 so' tha-t connec-` tion 17 vis open to exhaust thereby venting auxiliary valve chamber 19 and permitting valve 20 to be moved outwardly by the air in advance of piston 9 to uncover exhaust ports 23. The piston is thus able to deliver its blow with full force and entirely without back pressure.

It will be noted that when auxiliary valve 20 moves to its outward position shown in Fig. 2 stop 22a closes port 21 ,and in addition prevents the valve from entirely lclosing offA passage V18, so that when the control valve handle 8 is again returned to the-position shown in Fig. l the motive fluid admitted through connection 17 to passagev 18 has access behind the valve 2O to move it to the position shownin Fig. 1. The sealing of port 21 by stop 22a is important since it prevents finitial escape of pressure fluid directed tothe auxiliary valve chamber thereby using the 'full ower ofthe fluid to overcome inertia and friction'as well as the tendency of the -valve to stick. Thus movement of valve 20 is insured even 'if control handle 8 is moved slowly in the rearwarddirection. If the tool isnot to be operated while connected to a source of fluidsupply the control handle is moved to neutral position lmidway between lthepositions-shown inFigs. 1 and 2.v

From'the` above'itwill be apparent that the exhaust port-s 23 at the forward end of the piston chamber permit free exhaust of the air 'in'.jadvanceof the piston on the latters 4working stroke, that on the return stroke of -thepiston'exhaust ports 23 are closed'by the movement-of auxiliary valve`20 produced by .the-motive fluid 'admitted'bythe main control valve for the-rearward stroke of the piston Hso-th'at only ya small amount of motive fluid f is 'required "forthis purpose, and that the .parts producing the-new operative arrangement are simple, inexpensive tov manufacture andv assemble and well able to withstand t-he :hard'usage to which such tools are subjected vwithout getting out oforder. Y

While a preferred form of the invention vhasbeen herein shown and described, it is vl'to be yunderstood that'the invention is not "limited to the specific details thereof but coviers all changes, modifieationsand adaptations within thescope of the appended claims.

I fclaim as my Ainvention 1. A `fluidpres'sure hammer comprisingv a cylinder providing a piston chamber, a piston Ireciprocable'therein,'a valve, ports and passages directly controlled by said valve for supplying lpressure fluid to and venting yit 'from'the rear end of said piston chamber, a `vent-port for the front end of the piston chamber, and an auxiliary valve controlling I"said ventport andarranged to admit motive fluid released by saidA first named valve to the piston chamber for the rearward stroke of the piston.

`2. A fluid pressure 'hammer comprising fa cylinderproviding apiston chamber, a .pis-

valve arranged directly to control the supply of pressure fluid to and the venting of it from the rear end ofthe piston'chamber, and an auxiliary valve controlling a vent for the front end of the piston chamber and providing a single port of restricted size to admit motive fluid to the piston chamber to effect the rearward stroke of the piston.

4:. A fluid pressure hammer comprising Ya cylinderproviding a'piston chamber, a piston 'reciprocable therein, a manually operable valve for controlling the movements of the piston, a valve chamber adjacent the forward end of said cylinder connecting with the piston chamber and having a vent port for the latter, a conduit extending to saidV valve chamber under control of said valve, and an auxiliary valve in said'chamber for controlling said vent port,fsaid auxiliary valve being moved to cover said portby pressure fluid admitted to the valve chamber by said conduit and being moved to uncover said port by the Vair in advance of the piston on its `working stroke.

5. A fluid pressure hammer comprising a cylinder providing a piston chamber, apisyton reciprocable therein, a manually operable valve for controlling the movements of the piston, a valve chamber adjacent the forward end of said cylinder connecting with the pistonchamber and having a vent port for the latter, a conduit extending to said valve chamber under control of said valve, and an auxiliary valve in said chamber for controlling said vent port, said auxiliary valve being moved-to cover said port by pressure fluid advmitted to the valve chamber by said conduit and being Vmoved to uncover said port by the air in advance of the piston on itsworking stroke, said auxiliary valve being arranged to admit to the piston chamber to effect the rearward stroke of the piston a portion of the motive fluid entering said valve chamber.

6. A fluid pressure hammer comprising a cylinder'providing a piston chamber, a piston reciprocable therein, a manually operable valve for controlling the movements of the piston, a valve chamber adjacent the forward end of said cylinder connecting with the piston chamber and having a vent port'for the latter, a conduit extending to said valve chamber'under control of-said valve, and lan retain a 'auxiliary `valve in said chamber for controlling said vent port, said auxiliary valve being moved to cover said port by pressure fluid admitted to the valve chamber by said conduit and being moved to uncover said port by the air in advance of the piston on its working stroke, said auxiliary valve having a restricted port for admitting to the piston chamber a portion of the motive fluid enterin sai-d valve chamber.

g. A fluid pressure hammer comprising a cylinder providing a piston chamber, a piston reciprocable therein, a manually operable valve at the rearward endof said cylinderV for controlling the movements of the piston, a4

valve chamber opening into the forward end of said piston chamber, a passage leading to said valve chamber under control of said valve, a cup valve movable in said valve chamber, vent ports for the piston chamber controlled by said cup valve, said cup valve having a port establishing connection between sai-d valve chamber and the piston chamber, sai-d valve port being smaller than the passage leading to said valve chamber to predominating pressure in said valve chamber.

8. A fluid pressure hammer comprising a cylinder providing a piston chamber, a piston reciprocable therein, a manually operable valve for controlling the movements of the piston, an open-ended valve chamber communicating with the forward end of the piston chamber, a closure for the outer end of said valve chamber, a passage leading to said chamber under control of said valve, said valve chamber having vent ports for the piston chamber, an auxiliary valve in said valve chamber controlling said vent ports, said auxiliary valve having a port there- .through and a stop on said closure for limiting the movement of said auxiliaryI valve in one direction and for controlling said last named port. p

9. A fluid pressure hammer comprisinga cylinder providing a piston chamber, a piston reciprocable therein, a manually operable Valve for controlling the movements of the piston, an open-ended valve chamber communicating with the forward end of the piston chamber, a closure for the outer end of said valve chamber, a passage leading to said chamber under control of said valve, sai-d valve chamber having vent ports for the piston chamber, an auxiliary valve cylindrical in shape reciprocable in said valve chamber to control said vent ports, said auxiliary valve having a transverse wall with a singler port therethrough arranged to communicate with the piston chamber, said port being of' less cross sectional area than said passage.

10. A fluid pressure hammer comprising a cylinder providing a piston chamber, a piston reciprocable therein, a manually operable valve for controlling themovements of the piston, an open-ended valve chamber communicating with the forward end of the piston chamber, a closure for the outer end of said valve chamber, a passage leading to said chamber under control of said valve, said valve chamber having vent ports for the piston chamber, an auxiliary valve cylindrical in shape reciprocable in said valve chamber to control said vent ports, said auxiliary valve having a transverse wall with a port therethrough, and a stop on said closure arranged to engage said valve to limit its movement in one direction and to close said port.

11. A fluid pressure hammer comprising a cylinder providing a piston chamber, a piston reciprocable therein, a manually operable valve for controlling the movements of the piston, an open-end-ed valve chamber vcommunicating with the forward end of the piston chamber, a closure for the outer end of said valve chamber, a passage leading to said chamber under control of said valve, said valve chamber having vent ports-for the piston chamber, a cup valve reciprocable in said valve chamber to control said vent ports and having a port therethrough, and a stop on said closure for engagement with said cup valve to prevent closing of said passage by .said cup valve and for controlling said last named port.

12. A fluid pressure hammer comprising a cylinder providing a piston chamber, a back head secured to sai-d cylinder, a manually operable valve in said head for controlling the movements of the piston, a front head on said cylinder, an open-ended valve chamber in said front head opening into the piston chamber, a conduit under control of said valve leading to said valve chamber, vent ports for the piston chamber opening into said valve chamber, a cup valve within said valve chamber controlling said vent ports and arrange-d to be thrown to cover said vent ports by motive fluid admitted by said conduit and in the other direction to uncover said vent ports by air in advance of the piston on its working stroke, a port in said cup valve of less area in cross section than the area of said conduit for directing a portion of the motive fluid from said conduit into said piston chamber to 'drive the piston on its rearward or non-work- 

